Patent Literature 1 proposes that, when a columnar workpiece is sliced into thin boards by wire electric discharge machining, one wire electrode is wound around a plurality of guide rollers to be arranged in parallel to each other, thereby forming a large number of cutting wire portions, a voltage is fed to the cutting wire portions individually, and electric discharge is generated between the cutting wire portions and the workpiece at the same time, so that the productivity of the slice machining of the workpiece is improved.
According to an electric discharge wire saw of the configuration described above, when the machining advances and a machined groove formed in a workpiece becomes deeper, it gradually becomes difficult to discharge machining chips from the machined groove, and the machining chips remain in the machined groove. If the machining chips remain in the machined groove, the frequency of electric discharge from cutting wires to the machining chips becomes high, electric discharge in a machining direction is reduced and thus the machining speed is reduced. Furthermore, when electric discharge in a groove-width direction is increased, the width of the machined groove is increased, and it becomes difficult to reduce a slice pitch. Further, the probability of wire breakage of the cutting wire increases, and a machining surface is easily damaged due to the breakage of the cutting wire. Even when the disconnected portions of the wire are tied to each other and machining can be resumed, because a removed amount is large at the portion of the wire breakage, there is a problem that a member having its slicing being completed needs to be additionally subjected to a grinding process including a damaged region of the disconnected portion, and a needless time for machining and loss of members occur. Therefore, Patent Literature 2 discloses a technique in which machining liquid is sprayed to a machined portion by using a nozzle, machining chips generated during the machining are discharged outside from the machined groove so that the machining chips do not remain in an electrode gap. Patent Literature 3 discloses a technique for supplying machining liquid to machined grooves.